The present invention relates to mechanisms for automatically opening and closing doors. More particularly, the present invention relates to a microcontroller system utilized to control the mechanism for opening and closing a door which senses an obstruction in the path of the moving door and reacts thereto.
Microcontrollers are often utilized to control a mechanism which automatically opens and closes a door. Power is normally supplied to an electric motor which is mechanically linked to the door mechanism to propel the door in an open or closed direction. The supply of power to the electric motor can be regulated by a microcontroller. The microcontroller will regulate the opening and closing speed and the direction of door travel depending upon a preprogrammed sequence. Generally, a door operated in such a manner will follow a preprogrammed velocity profile in both the opening and closing sequence.
FIG. 3 shows a graph which illustrates a representative example of a standard velocity profile for an automatically opened or closed door where the parameters on the horizontal and vertical axes have the followings:
The graph in FIG. 3 illustrates how a door starts at a stationary or the minimum velocity, quickly accelerate to a maximum velocity (Vmax) and maintains this velocity throughout the travel from the closed to the fully open position. Once in the fully opened position the velocity drops immediately down to the minimum again. This sequence is also repeated for the closing of the door where the door starts at rest position quickly accelerates to maximum velocity and then returns to rest position upon full closure.
When the door is travelling at maximum velocity either opening or closing, it can encounter obstructions which are unknowingly placed in the path of travel of the door. When a door encounters such obstructions, damage can result to the door, to the obstruction or to both. Therefore, means must be provided for stopping the travel of the door and or reversing such travel if necessary and/or to minimize potential damage.
Further, changes in the travelling velocity of the door can also result from non-obstruction sources. Factors within the door mechanism itself such as friction, mechanical wear, power supply disturbances, drive mechanism irregularities and the like, can cause the door to experience acceleration or deceleration during its travel. It is important that the door control mechanism is able to differentiate between these internal factors and external obstructions. The mechanism must not respond to any of these internal factors as if they were obstructive interference. If the control mechanism were to so react, the door will be stopped and/or reversed unnecessarily.